In order to transport granular materials they are often entrained in air or some gas. By fluidizing granular material in air, one is capable of transporting the granular materials through pipes, long distances to desired locations. Once the material has reached its desired location, the material being transported must be separated from the air which is usually accomplished with a cyclone. Therefore in most material conveying systems using air fluidization or entraining granular particles within air, the final air material separation is often accomplished with a cyclone.
Furthermore, there is often the requirement that the granular materials being transported, further needs to be classified into different sizes. The most fundamental classification that usually is required is separation of coarser material from finer material for subsequent operations. There are a number of existing devices which independently of the cyclone have the capability of classifying materials into different sizes. It would be desirable, however to use the cyclone in addition to its air separating ability to also be able to classify the materials into different sizes. This would eliminate an intermediate step and the equipment associated with classifying granular materials into various sizes.
There have been attempts at accomplishing this within the cyclone, in for example prior art in International Application WO 03/033158 A1, titled Dust Separator, filed by Rapid Granulator AB on Oct. 19, 2001, wherein they describe a cyclone which is used for the separation of dust from granular material, using a separator chamber mounted on the lower side of a cyclone. Particles dropping out of the bottom of the cyclone pass into a separator chamber and impinge upon a deflector device, wherein via this impact any dust upon the particles settling out of the bottom of the cyclone is dislodged and carried upward through a “inner wall” of the cyclone. Further, the art teaches plates disposed within the inner walls, whose purpose is to prevent or reduce rotation of the flow which takes place with the major direction upwards within the “inner wall” of the cyclone. An air inlet is located below the separator chamber. A downwardly angled portion of the inlet conduit, introduces air and is controlled by a regulator valve. The art taught in this patent is directed towards removal of dust which is adhered to larger granular particles. The apparatus intends to dislodge the dust from the larger granular materials by impinging the larger granular materials upon the deflector devices within a separation chamber. This unit is limited to the collection and removal of extremely fine dust particles from granular materials.
There is however, a need to be able to use a cyclone as a material classifier to be able to classify granular materials into coarse and fine in addition to having the capability of dust removal as indicated in the prior art PCT Application WO 03/033158 A1.